This invention relates generally to injection molding and more particularly to a method of making a heated injection molding nozzle with a tip insert.
As seen in the applicant's U.S. Pat. No. 4,557,685 which issued Dec. 10, 1985 and U.S. Pat. No. 4,768,283 which issued Sep. 6, 1988, injection molding nozzles having a tip aligned with the gate to provide hot tip molding are well known. Apparatus having a hot tip provided by a torpedo seated in the front end of a nozzle is also known. For instance, the applicant's Canadian Patent Application Number 2,082,700 which was laid open May 13, 1994 shows a torpedo having a tip held in place by a nozzle seal which slides into a seat in the front end of the nozzle. U.S. Pat. No. 5,658,604 to Gellert et al. which issued Aug. 19, 1997 similarly shows a torpedo with a tip which is held in place by a nozzle seal which is screwed into a seat in the front end of the nozzle. As seen in the applicant's U.S. Pat. No. 5,494,433 which issued Feb. 27, 1996, it is also known to have the tip provided by a side gate seal which screws into the nozzle.
As seen in U.S. Pat. No. 5,704,113 to Mold-Masters which issued Jan. 6, 1998, a method of making a nozzle wherein an inner portion, an outer collar portion and an electrical heating element are integrally brazed together is also known. The applicant's U.S. Pat. No. 5,437,093 which issued Aug. 1, 1995, shows a method wherein an injection molding nozzle is made by first brazing an inner core, an outer collar portion and an outer sleeve together by heating to a temperature above a first melting temperature and then casting an electrical heating element into the space between them by heating to a temperature above a second lower melting temperature.
The previous apparatus and methods have the disadvantage that the portion providing the tip is either screwed or pressure fitted into place and therefore does not provide optimal heat transfer.